As far as the performance software used for these calculations I believe it is the fully certified Airbus Flight Operations Virtual Environment (FOVE) software that is being used by most Airbus operators, including EK.
The system requires the pilot to select a specific airport and runway, input environmental data and TOW from which the speeds are then calculated. The TOW is usually derived independently from the FMS which works this out from the ZFW and Block fuel input made by the pilot. However, if an error is made in entering one of these figures into the FMS then the same problem would occur, an incorrect TOW would be derived from the FMS and input to the FOVE, resulting in incorrect speeds . It seems that when the aircraft is static on the ground, there is no way the aircraft can know it's own weight apart from pilot input. The last check is done on receipt of the load sheet when the take off weight can be verified, but history shows that this check has failed in the past as well.
The true weight only becomes apparent when the operation becomes dynamic and actual physics takes over. If Lift does not exceed Weight iregardless of what was entered in the computer, a/c does not fly.... pretty basic!! In other cases where similar but smaller errors were made, the problem became evident after lift off and V2 was inside VLS, but above Vs1g allowing a/c to get airborne and basically accelerate in ground effect to a safe flying speed.
Still room for development in this critical area of the operation and I believe the onus lies with the manufacturers and not with operators trying to develop clever SOP's to double and triple check figures. etc... The aircraft should be able to do it's own independent "weigh in" somehow and tell the pilots at door closure or first engine start if their entered figures are within a given tolerance allowing for safe flight.
Last edited by High 6; 20th Nov 2009 at 04:49.